Power converter

Abstract

A power converter including a series circuit of DC power sources, a series circuit of positive side and negative side reverse conducting semiconductor switches. The power converter also includes a forward diode and a reverse diode connected from a neutral-point power source terminal toward the positive side and negative side reverse conducting semiconductor switches, respectively. The power converter includes intermediate DC power sources connected to the neutral-point power source terminal for generating predetermined voltages between potentials of positive side and negative side power source terminals and the neutral-point power source terminal, respectively, and commutation circuits composed of a series circuit of a two-way semiconductor switch and a reactor connected between the positive side and negative side intermediate voltage terminals and the positive side and negative side conductive semiconductor switches, respectively. The power converter further includes a voltage change-rate suppressing capacitor connected between one of power source terminals, the neutral-point power source terminal, intermediate voltage terminals and one of connecting points of adjacent two of the reverse conducting semiconductor switches.

What is claimed is: 
     
       1. A power converter comprising: a series circuit of a positive side DC power source and a negative side DC power source connected at a neutral-point power source terminal;   a direction from an anode to a cathode being designated as forward direction and a direction from a cathode to an anode being designated as reverse direction:   a series circuit of a positive side first reverse conducting semiconductor switch and a positive side second reverse conducting semiconductor switch connected in series in said forward direction from a positive side power source terminal of said positive side DC power source toward an AC output terminal of said power converter;   a series circuit of a negative side first reverse conducting semiconductor switch and a negative side second reverse conducting semiconductor switch connected in series in said reverse direction from a negative side power source terminal of said negative side DC power source toward said AC output terminal;   a forward diode connected from said neutral-point power source terminal toward a cathode of said positive side first reverse conducting semiconductor switch in said forward direction;   a reverse diode connected from said neutral-point power source terminal toward an anode of said negative side first reverse conducting semiconductor switch in said reverse direction;   a positive side intermediate DC power source connected to said neutral-point power source terminal for generating a predetermined voltage between potentials of said positive side power source terminal and said neutral-point power source terminal at a positive side intermediate voltage terminal;   a negative side intermediate DC power source connected to said neutral-point power source terminal for generating a predetermined voltage between potentials of said negative side power source terminal and said neutral-point power source terminal at a negative side intermediate voltage terminal;   a first commutation circuit composed of a series circuit of a two-way semiconductor switch capable of controlling forward and reverse currents individually and a reactor, connected between said positive side intermediate voltage terminal and said cathode of said positive side first reverse conducting semiconductor switch;   a second commutation circuit composed of a series circuit of a two-way semiconductor switch capable of controlling forward and reverse currents individually and a reactor, connected between said negative side intermediate voltage terminal and said anode of said negative side first reverse conducting semiconductor switch; and   a voltage change-rate suppressing capacitor connected between one of said positive side power source terminal, said neutral-point power source terminal, said negative side power source terminal, said positive side intermediate voltage terminal and said negative side intermediate voltage terminal and one of connecting points of adjacent two of said positive side first reverse conducting semiconductor switch, said positive side second reverse conducting semiconductor switch, said negative side second reverse conducting semiconductor switch and said negative side first reverse conducting semiconductor switch.   
     
     
       2. The power converter according to claim 1, wherein said voltage change-rate suppressing capacitor includes: a first voltage change-rate suppressing capacitor connected between an anode and said cathode of said positive side first reverse conducting semiconductor switch; and   a second voltage change-rate suppressing capacitor connected between said anode and a cathode of said negative side first reverse conducting semiconductor switch.     
     
     
       3. The power converter according to claim 1, wherein: said voltage change-rate suppressing capacitor is connected between said neutral-point power source terminal and said output terminal.   
     
     
       4. The power converter according to claim 1, wherein said voltage change-rate suppressing capacitor includes: a first voltage change-rate suppressing capacitor connected between an anode and said cathode of said positive side first reverse conducting semiconductor switch;   a second voltage change-rate suppressing capacitor connected between said anode and a cathode of said negative side first reverse conducting semiconductor switch; and   a third voltage change-rate-suppressing capacitor connected between said neutral-point power source terminal and said output terminal.     
     
     
       5. A power converter comprising: a series circuit of a positive side DC power source and a negative side DC power source connected at a neutral-point power source terminal;   a direction from an anode to a cathode being designated as forward direction and a direction from a cathode to an anode being designated as reverse direction;   a series circuit of a positive side first reverse conducting semiconductor switch and a positive side second reverse conducting semiconductor switch connected in series in said forward direction from a positive side power source terminal of said positive side DC power source toward an AC output terminal of said power converter;   a series circuit of a negative side first reverse conducting semiconductor switch and a negative side second reverse conducting semiconductor switch connected in series in said reverse direction from a negative side power source terminal of said negative side DC power source toward said AC output terminal;   a forward diode connected from said neutral-point power source terminal toward a cathode of said positive side first reverse conducting semiconductor switch in said forward direction;   a reverse diode connected from said neutral-point power source terminal toward an anode of said negative side first reverse conducting semiconductor switch in said reverse direction;   a positive side intermediate DC power source connected to said neutral-point power source terminal for generating a predetermined voltage between potentials of said positive side power source terminal and said neutral-point power source terminal at a positive side intermediate voltage terminal;   a negative side intermediate DC power source connected to said neutral-point power source terminal for generating a predetermined voltage between potentials of said negative side power source terminal and said neutral-point power source terminal at a negative side intermediate voltage terminal;   a first commutation circuit composed of a series circuit of a two-way semiconductor switch capable of controlling forward and reverse currents individually and a reactor, connected between said positive side intermediate voltage terminal and said output terminal;   a second commutation circuit composed of a series circuit of a two-way semiconductor switch capable of controlling forward and reverse currents individually and a reactor, connected between said negative side intermediate voltage terminal and said output terminal; and   a voltage change-rate suppressing capacitor connected between one of said positive side power source terminal, said neutral-point power source terminal, said negative side power source terminal, said positive side intermediate voltage terminal and said negative side intermediate voltage terminal and one of connecting points of adjacent two of said positive side first reverse conducting semiconductor switch, said positive side second reverse conducting semiconductor switch, said negative side second reverse conducting semiconductor switch and said negative side first reverse conducting semiconductor switch.   
     
     
       6. A power converter comprising: a series circuit of a positive side DC power source and a negative side DC power source connected at a neutral-point power source terminal;   a direction from an anode to a cathode being designated as forward direction and a direction from a cathode to an anode being designated as reverse direction;   a series circuit of a positive side first reverse conducting semiconductor switch and a positive side second reverse conducting semiconductor switch connected in series in said forward direction from a positive side power source terminal of said positive side DC power source toward an AC output terminal of said power converter;   a series circuit of a negative side first reverse conducting semiconductor switch and a negative side second reverse conducting semiconductor switch connected in series in said reverse direction from a negative side power source terminal of said negative side DC power source toward said AC output terminal;   a forward diode connected from said neutral-point power source terminal toward a cathode of said positive side first reverse conducting semiconductor switch in said forward direction;   a reverse diode connected from said neutral-point power source terminal toward an anode of said negative side first reverse conducting semiconductor switch in said reverse direction;   a positive side intermediate DC power source connected to said neutral-point power source terminal for generating a predetermined voltage between potentials of said positive side power source terminal and said neutral-point power source terminal at a positive side intermediate voltage terminal;   a negative side intermediate DC power source connected to said neutral-point power source terminal for generating a predetermined voltage between potentials of said negative side power source terminal and said neutral-point power source terminal at a negative side intermediate voltage terminal;   a series circuit of a first two-way semiconductor switch capable of controlling forward and reverse currents individually and a reactor, connected between said positive side intermediate voltage terminal and said output terminal;   a second two-way semiconductor switch capable of controlling forward and reverse currents individually, connected between said negative side intermediate voltage terminal and a connecting point of said first two-way semiconductor switch and said reactor; and   a voltage change-rate suppressing capacitor connected between one of said positive side power source terminal, said neutral-point power source terminal, said negative side power source terminal, said positive side intermediate voltage terminal and said negative side intermediate voltage terminal and one of connecting points of adjacent two of said positive side first reverse conducting semiconductor switch, said positive side second reverse conducting semiconductor switch, said negative side second reverse conducting semiconductor switch and said negative side first reverse conducting semiconductor switch.   
     
     
       7. The power converter according to claim 5 or claim 6, wherein: said voltage change-rate suppressing capacitor is composed of a plurality of capacitors; and   each of said capacitors is connected between one of said positive side power source terminal, said neutral-point power source terminal, said negative side power source terminal, said positive side intermediate voltage terminal and said negative side intermediate voltage terminal and one of connecting points of adjacent two of said positive side first reverse conducting semiconductor switch, said positive side second reverse conducting semiconductor switch, said negative side second reverse conducting semiconductor switch and said negative side first reverse conducting semiconductor switch, respectively.   
     
     
       8. The power converter according to claim 5 or claim 6, wherein: said voltage change-rate suppressing capacitor is connected between said neutral-point power source terminal and said AC output terminal.   
     
     
       9. The power converter according to claim 5 or claim 6, wherein said voltage change-rate suppressing capacitor includes: a first voltage change-rate suppressing capacitor connected between said positive side intermediate voltage terminal and said output terminal; and   a second voltage change-rate suppressing capacitor connected between said negative side intermediate voltage terminal and said AC output terminal.   
     
     
       10. The power converter according to claim 5 or claim 6, wherein said voltage change-rate suppressing capacitor includes: a first voltage change-rate suppressing capacitor connected between an anode and said cathode of said positive side first reverse conducting semiconductor switch; and   a second voltage change-rate suppressing capacitor connected between said anode and a cathode of said negative side first reverse conducting semiconductor switch.   
     
     
       11. A power converter comprising: a series circuit of a plurality of DC power sources composed of a first DC power source through a n-th DC power source;   a plurality of positive side terminals of said DC power sources being designated as a first power source terminal through a n-th power source terminal, respectively;   a negative side terminal of said n-th DC power source being designated as a (n+1)-th power source terminal;   a direction from an anode to a cathode being designated as forward direction and a direction from a cathode to an anode being designated as reverse direction;   a series circuit of a plurality of positive side reverse conducting semiconductor switches composed of a positive side first reverse conducting semiconductor switch through a positive side n-th reverse conducting semiconductor switch connected in series in said forward direction from said first power source terminal toward an AC output terminal of said power converter;   said positive side first reverse conducting semiconductor switch connected to said first power source terminal being firstly operated in a plurality of said positive side reverse conducting semiconductor switches;   a series circuit of a plurality of negative side reverse conducting semiconductor switches composed of a negative side n-th reverse conducting semiconductor switch through a negative side first reverse conducting semiconductor switch connected in series in said reverse direction from said (n+1)-th power source terminal toward said AC output terminal;   said negative side n-th reverse conducting semiconductor switch connected to said (n+1)-th power source terminal being firstly operated in a plurality of said negative side reverse conducting semiconductor switches;   a plurality of forward diodes connected from said second through n-th power source terminals toward anodes of said positive side second through n-th reverse conducting semiconductor switches in said forward direction, respectively;   a plurality of reverse diodes connected from said second through n-th power source terminals toward anodes of said negative side second through n-th reverse conducting semiconductor switches in said reverse direction, respectively;   a plurality of intermediate DC power sources composed of a first intermediate DC power source through n-th intermediate DC power source connected to said second through (n+1)-th power source terminals for generating predetermined voltages between potentials of said first and second power source terminals through between potentials of said n-th and (n+1)-th power source terminals at a first intermediate voltage terminal through a n-th intermediate voltage terminal, respectively;   a plurality of commutation circuits composed of a first commutation circuit through a n-th commutation circuit, each composed of a series circuit of a two-way semiconductor switch capable of controlling forward and reverse currents individually and a reactor, connected between said first through n-th intermediate voltage terminals and an intermediate terminal, respectively;   a reactor connected between said intermediate terminal and said AC output terminal, and   a voltage-change rate suppressing capacitor connected between one of said first through (n+1)-th power source terminals and said first through n-th intermediate voltage terminals and one of connecting points of adjacent two of said positive side reverse conducting semiconductor switches and said negative side reverse conducting semiconductor switches.   
     
     
       12. The power converter according to claim 11, wherein: said voltage change-rate suppressing capacitor is composed of a plurality of capacitors; and   each of said capacitors is connected between one of said first through (n+1)-th power source terminals and said first through n-th intermediate voltage terminals and one of connecting points of adjacent two of said positive side reverse conducting semiconductor switches and said negative side reverse conducting semiconductor switches, respectively.   
     
     
       13. The power converter according to claim 11, wherein: said voltage change-rate suppressing capacitor is connected between one of said first through n-th intermediate voltage terminals and said AC output terminal.   
     
     
       14. A power converter comprising: a series circuit of a plurality of DC power sources composed of a first DC power source through a n-th DC power source;   a plurality of positive side terminals of said DC power sources being designated as a first power source terminal through a n-th power source terminal, respectively;   a negative side terminal of said n-th DC power source being designated as a (n+1)-th power source terminal;   a direction from an anode to a cathode being designated as forward direction and a direction from a cathode to an anode being designated as reverse direction;   a series circuit of a plurality of positive side reverse conducting semiconductor switches composed of a positive side first reverse conducting semiconductor switch through a positive side n-th reverse conducting semiconductor switch connected in series in said forward direction from said first power source terminal toward an AC output terminal of said power converter;   said positive side first reverse conducting semiconductor switch connected to said first power source terminal being firstly operated in a plurality of said positive side reverse conducting semiconductor switches;   a series circuit of a plurality of negative side reverse conducting semiconductor switches composed of a negative side n-th reverse conducting semiconductor switch through a negative side first reverse conducting semiconductor switch connected in series in said reverse direction from said (n+1)-th power source terminal toward said AC output terminal;   said negative side n-th reverse conducting semiconductor switch connected to said (n+1)-th power source terminal being firstly operated in a plurality of said negative side reverse conducting semiconductor switches;   a plurality of forward diodes connected from said second through n-th power source terminals toward anodes of said positive side second through n-th reverse conducting semiconductive switches in said forward direction, respectively;   a plurality of reverse diodes connected from said second through n-th power source terminals toward anodes of said negative side second through n-th reverse conducting semiconductor switches in said reverse direction, respectively;   a plurality of two-way semiconductor switches, each capable of controlling forward and reverse currents individually, composed of a first two-way semiconductor switch through a n-th two-way semiconductor switch connected between said second through (n+1)-th power source terminals and an intermediate terminal, respectively;   a commutation circuit composed of a series circuit of an intermediate DC power source, a two-way semiconductor switch capable of controlling forward and reverse currents individually and a reactor, connected between said intermediate terminal and said AC output terminal;   a voltage-change rate suppressing capacitor connected between one of said first through (n+1)-th power source terminals and one of connecting points of adjacent two of said positive side reverse conducting semiconductor switches and said negative side reverse conducting semiconductor switches.   
     
     
       15. The power converter according to claim 14, wherein: said voltage change-rate suppressing capacitor is composed of a plurality of capacitors; and   each of said capacitors is connected between one of said first through (n+1)-th power source terminals and one of connecting points of adjacent two of said positive side reverse conducting semiconductor switches and said negative side reverse conducting semiconductor switches, respectively.   
     
     
       16. The power converter according to claim 14, wherein: said voltage change-rate suppressing capacitor is connected between one of said first through (n+1)-th power source terminals and said AC output terminal.